Where money grows

Cities routinely rake up tens of millions of dollars from their urban forests annually in ways that are not always obvious. Leafy canopies lower summer air conditioning bills, but more shade also means less blade to maintain thousands of acres of grass. Health-wise, trees contribute to lower asthma rates and birth defects by removing air pollutants.

Portland, New York City, Milwaukee and Atlanta are among the cities that have quantified the payoff from pines and palms, olives and oaks. It’s part of a breakthrough in thinking among city planners in recent decades who now realize that a city runs not just on engineering, but on biology and ecology as well.